Control systems are often used to position a control object. Such control systems often utilize servo data in the form of positional indicia to detect the position of the control object. Depending on the configuration of the control system, the positional indicia can include both radial and angular values.
For example, in some data storage devices the servo data are embedded onto recording surfaces of rotatable storage media to define a number of adjacent concentric tracks (cylinders). User data are stored in data sectors defined along the tracks. A suitable addressing scheme is employed to enable a servo control circuit to identify the physical location of each of the various sectors, so that the transducer can be moved thereto to carry out a requested data I/O operation.
The servo data can indicate radial position such as in terms of identifying a particular track address, and angular position such as along the track with respect to a once-around index (0° reference) point. A disadvantage of some existing control systems, however, is the inability to decode the angular position until the index point is actually reached.